High power pulsed lasers operate with output pulses of energy of various lengths or time duration. Typically the high powered pulsed CO.sub.2 laser operates with pulses in the region of 1-5 microseconds. Spatial variation in the output laser pulse occurs throughout the pulse for incremental changes of time during the life time of the pulse. It is desirable to have a detector which measures the peak power within a selectable cross section of the laser beam during the pulse period. It is also desirable to have a detector which measures integrated energy during the duration of the pulse in the beam.